I am considering gettng an Ooma device for my elderly parents who live in Vermont. As many people know, it snows a lot in Vermont which can cause the DSL they have to crash. They will only consider using Ooma if they can access 911 at all times. Can they integrate a landline for 911 only but have everythng else go through the VOIP system? In Vermot, even if a house does not subscribe to POTS phone service, the phone carrier needs to provide access to 911 for free as per state law. Is there a way to configure this?

Sure, you would just need to keep that 911 phone separate and have only that wire pair in the house wiring connected to the phone company at the demarc box. Use an isolated second wire pair for the Ooma phones. I'd test the no-service 911 function to make sure your understanding of how that's supposed to work is correct. Your parents would need to understand that they had a separate phone for 911 only.

Best possible phone for that 911 line would be a corded one. That way in case power goes down with the DSL they can still use the emergency phone. I keep a landline for financial reasons but I have a couple of corded phones on it since when the house goes dark in an outage I can still dial out to report a problem.